There are monkeys, Charles Darwin wrote in his book The Descent of Man, who "have a strong taste for tea, coffee, and spirituous liquors; [who] smoke tobacco with pleasure." And some of them, usually a small percentage, go too far. Here's Darwin's description of a group of monkeys waking up from a hard night of drinking.

On the following morning they were very cross and dismal; they held their aching heads with both hands, and wore a most pitiable expression: when beer or wine was offered them, they turned away with disgust, but relished the juice of lemons.

Modern examples are everywhere. This BBC video shows a bunch of monkeys hunting for refreshments at a hotel beach on the Caribbean island of St. Kitts. They can, if they like, suck on daiquiris and mai tais or they can choose Fanta orange soda. There is, of course, variation, but as the narrator explains, monkey drinking roughly parallels human drinking. Some of us drink a little. Some of us a lot. And the heavy drinkers suffer similarly.

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Drunk Worms

Some chemicals give pleasure. The problem is, in some of us, the natural urge for good times gets untamed. Then pleasure becomes a hunger that won't abate. "Alcohol can make male fruit flies hypersexual and pursue more same-sex mating, perhaps because the ethanol interferes with their reproductive signaling mechanisms," Dr. Barbara Natterson-Horowitz writes in her bestseller Zoobiquity. Even little worms get drunk. (They move more slowly and lay fewer eggs).

The book describes bighorn sheep in the Canadian Rockies who hunt for psychoactive lichen with such passion they "grind their teeth down to the gums scraping it off rocks. There are immature zebra fish, who when given a sprinkle of cocaine on one side of a fish tank, will stay on that [oh so promising] side for long periods, waiting for another fix."

Sick Or Slacker?

All animals are wired for pleasures that will lead them to reproduce, hunt for food, protect their young. The wiring is chemical and those chemicals are ancient. Humans have receptors for opiates in our brains, but so do insects, amphibians, and some of the Earth's oldest fish. And in every population, when the wiring gets overloaded, some animals can't get sober. Dr. Natterson-Horowitz says those animals are sick.

"These animal examples also challenge anyone who would stigmatize addicts or moralize about the disease," she writes. "What you might see as a personal failing in your no-account uncle who ruins every Thanksgiving with his drunken antics is not a uniquely human impulse."

True, but humans (I might argue) have reason, foresight and the ability to correct behavior we know is self-destructive. Other animals can't.

Dr. Natterson-Horowitz has this answer: "True, Uncle Bill can choose between a trip to the liquor store and a trip to his AA meeting. But if a fruit fly had the same option, it too, might sometimes take a rain check on sour coffee in a Styrofoam cup in favor of a warm, soothing hit of ethanol."

Yes, we have our weak moments. We all do. In non-human species, the problem seems a little bit sadder.

Case in point, she writes:

In Tasmania, a leading producer of medical opium, users sometimes sneak into the fields. Ignoring security cameras, they hop fences and gorge on poppy straw and sap. Dosed on the drug, they flail around in circles, damaging crops. Sometimes they pass out in the fields and have to be carried away in the morning. And there's no way to prosecute these trespassing scofflaws, no rehab to send them to. Because these freeloading opium eaters are wallabies.